Really annoying audio interference issue

Fire Lancer

Jun 8, 2010
This keeps coming up with different devices and is really annoying.

Firstly there was my as of yet unresolved issue with USB audio ( ) and now I have run into an issue when connecting the line out of one device (laptop) with the line in one my desktop :( Although this time I was thus able to record exactly what it is...

edited to remove suspect audio link -- Moderator

But connecting my desktops line out to it's own line in (with the same cable) yields no interference :(

My laptops and desktops audio out has no interference issues when connected to speakers, headphones, etc (with the exception of the usb varieties...) ....

Laptop -> USB audio - interference
Desktop -> USB audio - interference
Laptop -> Speakers - fine
Desktop -> Speakers - fine
Laptop -> Desktop line in - interference
Desktop -> Desktop line in - fine

So I am really out of ideas here, since each component excluding the previous USB audio problem seems to work fine some cases...


Simple, you posted an audio recording, the sound of the "interference" on a website that downloads junk software into the computers, without permission, of those who visit the site. No doubt this software is a spyware program, or worse.
Websites like this should be avoided, always. Never allow a site such as this to download crap into your computer.
As a condition of listening to the audio recording, I am required to allow (?) to load crap into my operating system.--Won't Happen!

If you post the audio recording on a site that does not attempt to load garbage into my computer, I will listen to it, and possibly help solve the problem. Or you can post it as a windows audio file.
But please refrain from posting links to sites that promise to "fix" my computer with garbage downloads.


Oct 15, 2007
its probably ground noise because the laptop has an inferior ground.
the same thing happens with my laptop when i connect it to my headunit in the car.
but listening with headphones doesnt make the noise.
and using a usb mp3 player doesnt make the same noise.

you would need something between the laptop and desktop that has a 'ground lift' switch.
but chances are you wont find one for a price of simply wanting the ground lift switch.

a ground loop isolator might work, but they usually degrade the sound.

Fire Lancer

Jun 8, 2010
Could you explain some of that please?

AFAIK the laptop and desktop share a common ground through the same 13A?

EDIT: Also wouldn't a ground problem result in a completely constant hum, and how would the same interference occur on a USB device connected solely to the device (ie no external power)?


Oct 15, 2007
i havent listened to the audio you recorded.. and after what was said about the website, i am not going to either.
a ground problem generally does cause a constant hum.
if your hum isnt constant, i have no idea.

youtube works wonders.

you dont need a video to upload audio.
just use windows movie maker to upload a blank screen with text.

i really cant help you any further with the situation.

Fire Lancer

Jun 8, 2010
so does no one have a place that will except things like audio files that they do like? I cant exactly afford to go buy webhosting or something just to put that on :(


Oct 15, 2007

thats the same thing my laptop does.
the sound is either the chipset or the main processor.
i can make it change by double clicking on something and putting a load on the processor.

i dont know if its a ground loop or if there is a lack of voltage filtering.
either way, its a disturbance of another circuit connected to the same power supply.
that 'other' circuit might be first in a chain of events, therefore what you are hearing is excess voltage 'bleeding' or 'spilling' into another circuit.

the fact that you can hookup the desktop's output into its own input suggests that there is no interference in the voltage of the desktop soundcard.
whatever that USB device is.. it doesnt have a proper circuit to keep itself isolated.
and usually a usb device wont have a circuit specifically designed to isolate itself electrically from whatever it is connected to unless there is a 'lift switch'
sometimes called a 'ground switch'
sometimes called an 'earth switch'

instead of the electricity being clean and pure.. there are spikes or fluctuations caused by either northbridge, the southbridge, or the main CPU.
the spikes need capacitors that can dull those spikes.. which eliminates the noise.

imagine you have voltage going to the northbridge.. and the northbridge uses what is needed and the voltage continues on to the soundcard.
without any power filtering capacitors, the voltage is going to go down whenever the northbridge drinks up some electricity and then the pressure spikes up whenever the northbridge stops drinking the electricity.

the reason speakers dont have the same interference on headphones is because there isnt a second power supply.
often times you dont hear the interference unless one source of electricity is blending / mixing with another source of electricity.
there is a push and pull relationship between the two power sources and that can cause the waves / fluctuations to come back.
IF there are power filters.. but they are being faced with waves / fluctuations .. the caps can lose their ability to remain stiff.
its like walking.. but you have your arms out and you are leaning from side to side trying not to completely fall over.
when you are dealing with sensitive electronics, simply putting one foot in front of the other is not enough.
walking on the edge of your shoe is enough to cause dramatic problems.

you need a USB audio device that can filter the interference.
maybe one with an electricity isolator.
maybe choosing an alternative method of powering the USB device would work.
maybe you can find a USB adaptor that isolates the two devices being connected.

and if you are really tech savvy or good with a soldering iron.. maybe you should disconnect the power pins from the usb socket and choose to power the USB device with 5 volts from a different source.

if you are not really tech savvy.. the electricity in your laptop is like water, and there is something inside the computer that is drinking that water and backwashing in it.
capacitors .. or 'stiffening caps' will stand there with their hand on somebodys chin, so that whenever somebody is done drinking, the cap will push the mouth closed so there is no backwash.

there is obviously a difference between closing the jawbone and sealing the lips.
choose your capacitors wisely.

you might be able to take your laptop and USB device to an electronics repair shop and ask them to modify the circuit so there isnt anymore interference.
but you have to trust the people to check circuit impedance and use new components that wont shorten the lifespan of the rest of the circuit.
laptops are supposed to run on DC current.
DC is pure and constant.
AC current is the one that flutters like bird wings at 60hz
and usually AC current is transformed into DC current immediately after entering the product at the power plug.

an electronics repair shop might tell that excess voltage to exit.. but it could cause too much voltage to exit and the entire system is thirsty for voltage.
its usually best to stack up the power so that the extra power is there if/when needed.
but just like a turbo on a car.. if there is no blowoff valve, you are gonna have lots of pressure with no where to go.
that extra electricity will start to raise voltages once the stacks fill up.. and that could damage something.

i have had audio interference like that on my laptop when connecting to my radio in the car via the auxilery port.
and if i use a USB soundcard.. the same thing happens because the USB soundcard gets its power from the laptop .. and there is no power filtering.
its kinda cute because i have a power inverter connected to the same car battery that the radio is connected to.
then the laptops power adapter plugs into the power invertor.
in my case, it could be the laptop itself, it could be the power adaptor, and if neither one of those have power filtering, it could be coming from the power inverter.

i never ever did buy a battery for my laptop.. but if you have one, you could try running the laptop off of the battery and see if the problem goes away.
it would be a temporary fix until you look into something that is dedicated towards electrical isolation of the usb socket.
the reason why it works (if and when it does) is because the battery circuit should have some extra power filtering.. OR the electricity that the battery provides isnt as chaotic compared to plugging the laptop into the power inverter.
therefore the weak power filtering already there will be enough to stop the voltage spiking.

and hey..
it might not be the electricity that is running through the circuit board.
there might be an electrical component that is too close to another electrical component and one of the components is leaking static and causing the noise.

maybe a self-powered USB hub will break the electrical connection and feed the USB audio device clean power.
maybe the interference is being injected into the audio output.

i think an electrical repair guy would use an oscilloscope to visually see what you are hearing.
and they might use some kind of device that is sensitive to static to see if there is any electricity radiating from a component on the circuit board.

i dont want to tell you that there is nothing you can do about it.
but you need to know one solution might not work because the problem is elsewhere.

you said the USB audio device connected to the laptop makes the same interference..
algebra tells me that the problem is with dirty voltage.
and the only two ways to fix that are:
get a power filter that connects inbetween the laptop and the USB audio device
use a self-powered usb hub that disconnects the electricity of the laptop and uses its own electricity from its own power adaptor.

a self-powered usb hub may or may not eliminate the problem.
because there are four wires in a usb socket.
two of them are 5 volt electricity wires .. two of them are data wires.
IF the problem is severe, the interference will be sent across the data wires.
and that means your usb controller is sending and receiving data even though there is all that electrical chaos going on.
if the usb data is at a different frequency and/or amplitude.. its relatively easy for the usb controller to continue without 'listening' or 'hearing' errors.
maybe the extra voltage on the usb controller is causing it to run hot.. which might make the controller die early.

okay.. now for the biggest thing.
the laptop might have done this when it was new.. and the designers have already known about it and compensated for it so nothing dies early.
(maybe they left it like that so it dies early on purpose)
but its possible that the components on the circuit board have grown old and weak.. which started to make the interference.

for people who enjoy electricity.. this situation would make them feel like a kid in a candy store.
there are many options and if you dont try each one, you wont know which one is the best solution.

i am not an electrical repair person.
i have had no training.. i am using logic and reasoning.
but i suppose my interest in electronics have helped me setup a virtual repair table based on what can and cant happen.
i've payed attention in science class when learning about electricity.
but i have no hands on experience doing these things myself.
i simply use my brain and view the problem in my head.. then come to a conclusion based on what can and cannot happen.
i have done some reading since i am interested in electronics.
and interference is not a very rare thing.. it is often asked about.

people in the electronics industry know about the interference.. which is why your usb controller isnt totally confused from listening to electronic interference.
one solution to the problem might be a filter that strips the audible frequency from the signal and leaves everything else the way it is.
kinda like a crossover that strips the bass from audio and lets the midrange and treble play.

replacing or modifying a power filter isnt something any untrained person can do.
but trying to avoid the problem is something anybody can do.
so again..
try running the laptop on the battery (if you have one and if the battery holds a charge)
or try to seperate the laptop power supply from the USB device with a self-powered usb adaptor.

i really dont know if all self-powered usb adaptors break the connection.
what should happen..
the 5 volt supply from the laptop usb socket plugs into the usb hub and the hub doesnt use the pins that carry the 5 volts.
instead, it simply reads from the data pins and channels power from its own power supply into the sockets that are used to split the usb socket.

i'd say good luck only because there is more than one possible problem and more than one way for the possible solution to fail.
its a hit or miss situation.. so if you aim, you might miss.
the soundcard on the laptop will probably always have the problem unless you take apart the laptop and filter the voltage going to the laptop.
but if the interference is caused by something that is too close to the sensitive soundcard.. you have to replace whatever is too close with something that wont do the same thing.

i was wanting to get a USB microphone preamp.. and i havent completely come to terms with having the same problem you have.
a high quality USB device meant for audio should filter the electricity before using it to avoid such interference from entering the audio path.

i have windows xp and movie maker wouldnt save the videos in 720p or 1080p
but after doing a search on the web.. i came across an article that lets you download high definition profiles.
the article went on to tell me where to put the files so that they could be used.

i know your video didnt have any actual video.. but you can still benefit uploading a high definition video because the audio quality is higher when selecting a high definition version of the video on youtube.
not really important now.. but you might find it useful in the future :)

Fire Lancer

Jun 8, 2010
So by using a 1080p image from pain? I get better audio quality....

Anyway, so that possibly explains the USB problem (since the data is I'm guessing digital, and things like my external HDD manage I'm guessing that can't be the problem there), will look for some kind of self powered hub...

But what about with just the desktop -> laptop stereo lead? Why does connecting directly to the speakers work fine, but connecting to my desktop (to allow both to use the same speakers) result in this problem (and the same interference pattern as with USB as well...)? The speakers have their own power source which is used to amplify the signal, so why should they be able to do that fine, but the desktop input can't handle it?


Oct 15, 2007
power isolation is being used.

hooking up the headphones shouldnt have any audio interference because there isnt a seperate power source.

amplified speakers have a circuit that isolates the power going to the amplifier.
if its isolated.. that means the laptop cant connect to it and spread the problem.

its like water.. if you give some direction, it will go that way unless there is something blocking it.

the desktop soundcard probably wont have the same power isolation.
the majority of filtering on a soundcard is to first filter the power received from the motherboard .. and then keep a storage of power for the digital to analog convertor so that the DAC never ever sucks on electricity from the motherboard.
the dacs are very sensitive to the electricity they are fed.

the analog to digital convertor on the soundcard is what is used when you use the record function.
that chip is designed to take electricity and turn it into 1's and 0's
because the chip is designed to take in electricity.. if you start to filter the electricity that is taken in, you will alter the sound being received.
you really have to have a complex circuit to filter out unwanted electrical noise and keep what isnt interference.

if you wanted to filter out the frequency heard in the interference.. a simple circuit would do that for the interference.. but then anything that uses the same frequency will also be filtered out.
which is why they dont try to remove the problem like that.
usually an electronic engineer will tell you to simply hunt down the problem and fix it before moving on.

the amplifier will take the audio signal and 'store it' then transfer it down the road and get amplified.
in this situation.. there are two instances that allow the amplifier to detach itself from the laptops interference.
first 'storing it'
then 'transfering it down the road'

its like saying you have some annoying friend that just wants to run and run .. then you say okay, if you want to run, i have a very long stretch of land that you can run on.
the annoying friend starts to run.. but gets tired and falls to the ground before reaching to the edge of the property.

its basically the same thing with the laptop electricity.
the interference wants to bleed out onto anything that is connected to it.. but the energy isnt strong enough to go on and on forever.
so as long as you give the interference enough room to die.. the problem goes away.

these are the basic principles of a ground loop and power filter problem.
the ground loop will spread onto anything it touches.. they are much more energetic.
they require a huge hole in the ground that the 'annoying friend who just wants to run and run' falls into and has no choice but to stop running.

both situations are a problem with excess power and that the power has no where to go.
its like being hyperactive in the house and you have nothing to do to help drain that energy.
its like having a bunch of parts on a circuit board designed to drink 5 volts but you are giving it 6 volts so there is an extra 1 volt floating around.
the parts wont convert that extra 1 volt into heat, therefore it is trapped and looking for a way out.

or its like having a bunch of parts on a circuit board that are designed to drink 5 volts but you are only feeding them 4 volts ... so the rest of the parts are in a state of being sucked on.

extra pressure or not enough pressure = bad things can happen.
smooth and relaxed is completely gone.

the amplifier's circuit has enough resistance to block the interference.
the headphones have enough resistance to block the interference.
the USB device doesnt have the resistance needed to stop the interference.
the soundcard in the desktop doesnt have enough resistence to stop the interference.

sometimes you can lose the interference simply because of the circuit traces on the circuit board (they are the lines that connect each piece to eachother)
when there isnt a whole lot of circuit traces.. like with a soundcard.. you have to build a circuit that is dedicated to adding resistance, or you have to pick a bunch of parts that have resistence of their own and hope they all add up to a resistence value high enough to block interference.

manufacturers build things with different price tags.
if you pay more, maybe then there will be something dedicated to blocking interference.
maybe that company doesnt offer such a feature into their design.. stating that they can cut cost down by not having the circuit and the price that they save can be put towards making the rest of the parts better.

it might be a thing of profit.. a company doesnt want you to know that the soundcard only costs $1.50 to make and they are making $10 profit for each soundcard that they sell.
the soundcard works unless you present it a problem.. then you get interference.
they dont necessarily have to fix the card so that you dont hear any interference.
they could say that there is a problem with whatever you are connecting it to.
because in a perfect world where all parts have no power filtering.. you dont have to worry about blaming a different piece of hardware as long as the main power supply is clean and the pieces of hardware that are connected to eachother are within the proper resistance values.

you can make a soundcard that works just fine with no noise.. but if the entire circuit's resistance is too high or too low, the FCC wont allow you to sell them because all they are gonna do is break something else.

the laptop motherboard might be the cause of the interference.. maybe it is the laptop's power adapter.
again.. maybe its because something has grown old and is now sensitive to the other parts around them.

the interference is going to want to run its course.
you can stop it from the source or allow it to drain itself of its energy.

you should be thankful that the speakers with the amplifier dont have the same problem.. because the amplifier is allowing the interference to drain itself of its energy before the signal reaches the amplifier.
IF the amplifier didnt allow the interference to drain itself to elimination.. then the interference would get amplified and played through the speakers.

this is why having a preamp can be so useful.
the signal doesnt get amplified at all when going through a preamp.
the preamp is there to allow any interference to drain itself to elimination before reaching the amplifier.
because if the amplifier gets it.. its not gonna care what is interference and what isnt, its just gonna amplify everything that is sent to it.

so what can be said here is that the laptop output doesnt have a preamp.
the desktop input doesnt have a preamp.
but the amplifier used with the speakers DOES have a preamp.

see.. a soundcard might send voltage that is the same as what a preamp might send, but it doesnt have the interference filters that a preamp has.

if you could picture a rather funny example:
you are running with weights on your ankles, as you run past the preamp your ankle weights are removed, and once you get to the amplifier - it is the sweat on your skin that has dried up and evaporated (which wont be amplified).


i just re-read your question and i missed something.
you said that you want to hook up the laptop and the desktop at the same time.
IF the speakers can connect to the laptop without any interference , and they can connect to the desktop without any interference..
then the reason why you are hearing interference with both of them connected at the same time is because there is twice as much voltage going into the speaker's amplifier.
the filters fill up with electricity before they can drain the interference.

hooking up two soundcards to one amplifier makes the resistance of the amplifier input drop down to half.. which might be enough to allow the interference to continue along on its way to the amplifier.


Oct 15, 2007
for what kind of link?

audio or usb?

i mean.. you can try a preamp for audio, but i think the general problems with preamps have been two things:
1. the filter isnt long enough to allow the interference voltage to drain and die.
2. the filter is long enough, but the parts used on the circuit board degrade the quality of the audio.. either by making the sound dull or by adding a 'coloring' effect to the sound.

usb choices are obvious.. but i dont know if they make anything with an actual filter.
you can isolate the power by using the self-powered hub.. but the interference might leak into the usb hub from the two data pins (not as likely though.. as this would indicate an almost nuclear meltdown of your laptops voltage supply)

if you are just gonna hookup the laptop to the desktops input and then use the desktop output to go to the speakers... try getting a Y-adapter and hook up the desktop output and laptop output to the speakers.
maybe the amplifier preamp will filter out the interference with both outputs connected.

otherwise getting a preamp to connect the laptop to the desktop is a rather expensive option.
you are starting to cross the line into audiophile and studio quality.


jeez.. i am looking at the preamplifier market and it states that the majority of preamps are being used as 'line drivers'
which is what car audio people know as to be an amplifier that takes the voltage from the RCA jacks on the back of the radio and amplifies them to 7-13 volts
that doesnt say anything about cleaning the signal though.

i went here:

i quickly read that the state of preamps has changed.
instead.. what makes the most sense is this:

it says that the buffer amplifier can 'buffer' the voltage OR the current.
what you need is a voltage buffer.
see the interference has voltage.. but it shouldnt have a whole lot of current.
the buffer amplifier would strip away some of the voltage from the signal.. and that would eliminate the interference, leaving only the audio.

either one of those is what preamps used to be back in the day.
now it seems they are split up into three categories.

BUT it says in that wikipedia page that the buffer amplifier changes the resistence so that the significant difference is bridged.
you dont necessarily need to have your output impedance changed a huge amount.
and if you go searching for a buffer amplifier, that is what you might find.

you probably need to stick around in the 'preamplifier' category and look for one that has noise suppresion or interference filtering or something along those lines.


Oct 15, 2007
as far as i'm concerned.. a resistor is simply a wire dipped in goop.
that goop has the amazing properties.

a resistor can strip voltage or current.
i wouldnt be suprised if a resistor stripped some current and holds the voltage at the same number.

if you are thinking about using a single resistor to try and eliminate the small current of the interference.. the sound quality might suffer.
having less amplitude is one thing.. but having less amplitude in some places and weird amplitude in other places .. it might be the 2nd most annoying thing you have to deal with.

audio transperency is a much desired characteristic.
but the resistors arent all made for audio.
there might be a specific combination of resistor and other parts needed to be connected together to get the optimum final result.

this is what electronic designers deal with.
they have to learn the pro's and con's of the part before they can start building a circuit.
like building with legos.. you have to know which piece to use to make a window in a wall.
if the piece is too short or too long, the window frame wont be perfect.

the high quality parts might not be available to the general public.. i dont know because i dont shop and buy parts to repair things.
i keep it simple and cannot afford to purchase dozens or even hundreds of resistors to try 'em out one by one.

Fire Lancer

Jun 8, 2010
So essentially there isn't a cheap/guaranteed solution :(

Well for the laptop->desktop, what about digital solutions, There is a 1Gb Ethernet link between the computers with just a hub in between (ping time is reported <1ms 99% of the time), could I have it send audio over that instead in some way?


Oct 15, 2007

i cant guarantee a cheap solution.. i would not know what to purchase or how to chain it together to form a circuit.

its possible to send audio over anything.. usb, ethernet, sata cable, ide cable.
but doing it that way isnt very common.. it would probably be some programmer's chance to fiddle around with their programming knowledge.

if i had to do something like that myself.. i would first have a look at VLC media player and try to use its media streaming option.
have a look here:

you install VLC player on the laptop as a server.
then you install VLC player on the desktop as a client.
the laptop will play the song and send it out to ethernet .. and the desktop will receive the data stream and play it.
i havent done it before, but i know its about as simple as setting up the server to stream and inputting the IP address of the laptop so the data stream can be received.

its a perfect solution that doesnt cost anything.
you can probably have the setup up and running after about an hour of reading the instructions.
the laptop will send the audio in a digital format.. possibly bypassing the soundcard entirely (depends on whether the soundcard has its own internal processor or not)
there wont be any (audible) interference sent the digital way.
if you want the laptop to play anything and everything, then send it to the desktop, you need to make sure you select the 'wave' setting in recording options.
'wave' will record anything and everything.. video games, movies, music, operating system sounds.

are you certain the hub allows you to send files back and forth between laptop and desktop?
if you have already made that happen, the VLC program has a track to run on.

i suppose if you are having trouble with the settings.. i could try to help.
but the program has its own forum and they would be able to tell you exactly what steps you missed (if it doesnt work the first time)

i know what its like to want something custom for your specific problem.. and using VLC seems like it is the most logical choice.


Mar 1, 2012

With regard to the noise you are experiencing from the audio output of your laptop, a product has been made by the Australian company ARX called a USB-DI. This device gives you a completly balanced output and features a ground lift switch to stop any noise. The unit plugs straight into your USB port and is found as a plug n play device. visit
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